The startup of engines fueled by a hydrocarbon based fuels such as gasoline, can exhibit the undesirable affect of discharging deleterious exhaust emissions or gases into the atmosphere. These exhaust gas emissions, prior to any predischarge treatment, usually contains environmentally unacceptable components as NO.sub.x, CO and unburned hydrocarbons.
It can be appreciated when one considers the number of automobiles in daily service, that the amount of untreated engine exhaust gas which is delivered into the atmosphere is virtually immeasurable. In spite of the number of catalytic converters presently in service which treat the gas prior to its discharge, the volume which flows past cold catalyst beds and consequently remains marginally treated, is still considerable. In brief, the present issue of a clean atmospheric environment suggests future air quality problems on a worldwide basis. Nonetheless, each step, even though minor, toward limiting the daily rate of pollutant gases which enter the atmosphere, must be welcomed.
One common practice known and accepted commercially for treating exhaust gases prior to their release into the atmosphere, is to convert the gases into less noxious fumes. A widely used and successful treatment for hot exhaust gas which leaves an automobile or truck engine at a temperature of up to 2000.degree. F., is to bring the gas into contact with an active catalyst to prompt the desired chemical conversion. This method is designed to receive and treat a steady flow of hot exhaust gas as it is being produced from an internal combustion engine.
Physically, even a brief contact between a heated catalyst material which should preferably be at least 700.degree. to 900.degree. F., and a stream of the engine exhaust gas, can be effective in achieving conversion of the gas into a less harmful condition. It is important to note however that this reaction, if utilized to its maximum potential, requires a preferred operating catalyst temperature in excess of about 900.degree. F.
It is known, for example, that for initial startup of any lo engine equipped vehicle having a catalytic converter, the catalyst will, in all probability, not be at a sufficiently high temperature to be effective. Thus, for the first several minutes or miles of the engine's operation, exhaust emissions will enter the atmosphere only marginally treated.
During a cold engine's startup period, the engine's exhaust gas becomes progressively hotter as engine parts become heated. As the initially produced gas contacts the catalyst, the latter will likewise become gradually heated from ambient, to the temperature of the gas. During this initial or warm-up period however, there will be minimal, if any, reaction in converting the exhaust gas to a less noxious state since the temperature of the catalyst is too low to promote a reaction. Subsequent to the warm-up period, however, due to contact of the hot exhaust gas stream with the catalytic bed, the latter will be heated to a temperature at which it is capable of achieving maximum effectiveness.